The present invention relates to silicone materials crosslinkable by addition of Si-bonded hydrogen at an aliphatic carbon-carbon multiple bond, processes for their preparation, platinum catalysts used for this purpose and the use of the crosslinkable materials.
Addition-crosslinking silicone materials crosslink by reaction of aliphatically unsaturated groups with Si-bonded hydrogen (hydrosilylation) in the presence of a catalyst, typically a platinum compound. Owing to the fact that the crosslinking reaction starts as soon as the essential constituents are simultaneously present, addition-crosslinking silicone materials have thus far been prepared almost exclusively as two-component formulations, the composition of the individual components being such that all three essential constituents are simultaneously present only after the individual components have been mixed together. Usually, one of the components contains the polyorganosiloxane having alkenyl functional groups and the platinum catalyst, and the other component contains the crosslinking agent having SiH functional groups, if necessary, in combination with further polyorganosiloxane having alkenyl functional groups. After mixing of the individual components, complete curing to give the silicone elastomer can be effected at room temperature, but is usually carried out at elevated temperature.
The use of two-component addition-crosslinkable silicone materials is associated with numerous disadvantages, such as, for example, logistics, the high risk of contamination by traces of platinum, and the necessity for an additional mixing step. Although a ready-to-use material is obtained after mixing of the components, it has only a limited pot life at room temperature. This necessitates, on the one hand, processing quickly following mixing, and, on the other hand, frequent cleaning of the storage container, metering units, processing machines, etc., since the material remaining, for example, through back-mixing or adhesion to the container walls, ultimately gels.
Because of these disadvantages, there have been many attempts to provide addition-crosslinking silicone materials as a one-component formulation (1C system). Since in the case of a 1C system all constituents required for the crosslinking are present together, the problem of suppressing premature crosslinking, which usually also takes place at room temperature, must be addressed. Possibilities for specifically controlling (increasing) the pot life of an addition-crosslinking material are sufficiently well known, for example through the use of inhibitors which are capable of considerably reducing the activity of the platinum catalyst at room temperature, such as, phosphorus compounds in combination with peroxides according to U.S. Pat. No. 4,329,275, or azodicarbonyl compounds according to EP-A-490 523. Although the pot life per se can be increased as desired through the type and content of such inhibitors, a disadvantageous effect on the crosslinking behavior is also inevitably associated with increasing pot life, particularly when the pot life is extended to several months by high inhibitor contents. Higher initiation temperatures and low crosslinking rate as well as undercrosslinking are the result in such cases.
A further possibility fundamentally differing from the use of inhibitors consists of encapsulating the platinum catalyst in a finely divided material which does not release the platinum until an elevated temperature has been reached. This can be effected, for example, by microencapsulation of the platinum catalyst with a thermoplastic silicone resin or an organic thermoplastic, as described, for example, in EP-A-363 006, which, however, is relatively expensive.
A third possibility consists in selecting, as the catalyst, specific platinum complexes whose activity is such that the hydrosilylation reaction takes place sufficiently rapidly at elevated temperature but to such a small extent at room temperature that pot lives of several months are achieved. Such addition-crosslinking materials containing platinum complexes were described, for example, in EP-A-583 159 and DE -A-36 35 236. Although the materials described have substantially improved pot lives with, in some cases, sufficiently high crosslinking rates, there is still a need for improving the pot life and crosslinking rate of addition-crosslinking materials formulated as a single component through use of more efficient platinum catalysts, without having to accept the abovementioned disadvantages.
The present invention provides addition-crosslinkable compositions containing aliphatically unsaturated compounds and Si-H-functional organopolysiloxanes together with unique platinum complexes which allow for extended shelf life as one-component addition-curable organopolysiloxanes, and extended pot life for two-component addition-curable organopolysiloxanes, without compromising crosslinking rates or levels.
The present invention thus relates to curable organopolysiloxane materials containing
(A) compounds which have radicals having aliphatic carbon-carbon multiple bonds,
(B) organopolysiloxanes having Si-bonded hydrogen atoms or, instead of (A) and (B) or in addition thereto,
(C) organopolysiloxanes which have SiC-bonded radicals having aliphatic carbon-carbon multiple bonds and Si-bonded hydrogen atoms, and
(D) a platinum catalyst selected from the group consisting of compounds of the formula 
and/or oligomeric or polymeric compounds which are composed of structural units of the general formula 
and optionally chemically bonded structural units of the general formula
R9rSiO(4xe2x88x92r)/2xe2x80x83xe2x80x83(VI)
in which
R2 denotes an optionally substituted diene which is linked by at least one xcfx80-bond to platinum and represents a straight or a branched chain having 4 to 18 carbon atoms or a cyclic ring having 6 to 28 carbon atoms,
R3 is identical or different and denotes a hydrogen atom, a halogen atom, xe2x80x94SiR43, xe2x80x94OR6 or monovalent, optionally substituted hydrocarbon radicals having 1 to 24 carbon atoms, with the proviso that, in the compounds of the formula (III), at least one radical R3 denotes xe2x80x94SiR43,
R4 is identical or different and denotes hydrogen, a halogen atom, xe2x80x94OR6 or monovalent, optionally substituted hydrocarbon radicals having 1 to 24 carbon atoms,
R6 is identical or different and is a hydrogen atom, xe2x80x94SiR43 or a monovalent, optionally substituted hydrocarbon radical having 1 to 20 carbon atoms,
R7 is identical or different and denotes a hydrogen atom, a halogen atom, xe2x80x94SiR43, xe2x80x94SiR4(3xe2x88x92t)[R8SiR9sO(3xe2x88x92s)/2]t, xe2x80x94OR6, or monovalent optionally substituted hydrocarbon radicals having 1 to 24 carbon atoms, with the proviso that, in formula (V), at least one radical R7 denotes xe2x80x94SiR4(3xe2x88x92t)[R8SiR9sO(3xe2x88x92s)/2]t,
R8 is identical or different and denotes oxygen or divalent, optionally substituted hydrocarbon radicals having 1 to 24 carbon atoms, which may be bonded to the silicon via an oxygen atom,
R9 is identical or different and denotes hydrogen or an organic radical,
r is 0, 1, 2 or 3,
s is 0, 1, 2 or 3 and
t is 1, 2 or 3.
Within the scope of the present invention, the term organopolysiloxane is intended to include polymeric, oligomeric and dimeric siloxanes.
If R2 is a substituted diene or the radicals R3, R4, R5, R6, R7 and R8 are substituted hydrocarbon radicals, preferred substituents are halogen atoms such as F, Cl, Br and I, cyano radicals, xe2x80x94NR62, heteroatoms such as O, S, N and P, and groups xe2x80x94OR6, in which R6 has the abovementioned meaning.
The compositions according to the invention may be one-component organopolysiloxane materials as well as two-component organopolysiloxane materials. In the latter case, the two components of the materials according to the invention may contain all constituents in any desired combination, in general with the proviso that one component does not simultaneously contain siloxanes having an aliphatic multiple bond, siloxanes having Si-bonded hydrogen and catalysts, i.e. essentially not simultaneously the constituents (A), (B) and (D) or (C) and (D). Preferably, the compositions according to the invention are one-component materials.
The compounds (A) and (B) or (C) used in the materials according to the invention are known to be chosen in such a way that crosslinking is possible. Thus, for example, on average, compound (A) has at least two aliphatically unsaturated radicals and siloxane (B) has at least three Si-bonded hydrogen atoms, or compound (A) has at least three aliphatically unsaturated radicals and siloxane (B) has at least two Si-bonded hydrogen atoms, or siloxane (C) which has aliphatically unsaturated radicals and Si-bonded hydrogen atoms in the abovementioned ratios is used instead of compounds (A) and (B).
The compound (A) used according to the invention may also be silicon-free organic compounds preferably having at least two aliphatically unsaturated groups, and organosilicon compounds having preferably at least two aliphatically unsaturated groups. Examples of organic compounds which can be used as component (A) in the materials according to the invention are 1,3,5-trivinylcyclohexane, 2,3-dimethyl-1,3-butadiene, 7-methyl-3-methylene-1,6-octadiene, 2-methyl-1,3-butadiene, 1,5-hexadiene, 1,7-octadiene, 4,7-methylene-4,7,8,9-tetrahydroindene, methylcyclopentadiene, 5-vinyl-2-norbornene, bicyclo[2.2.1]hepta-2,5-diene, 1,3-diisopropylbenzene, polybutadiene containing vinyl groups, 1,4-divinylcyclohexane, 1,3,5-triallylbenzene, 1,3,5-trivinylbenzene, 1,2,4-trivinylcyclohexane, 1,3,5-triisopropenylbenzene, 1,4-divinylbenzene, 3-methyl-1,5-heptadiene, 3-phenyl-1,5-hexadiene, 3-vinyl-1,5-hexadiene and 4,5-dimethyl-4,5-diethyl-1,7-octadiene, N,Nxe2x80x2-methylenebis(acrylamide), 1,1,1-tris(hydroxymethyl)-propane triacrylate, 1,1,1-tris(hydroxymethyl)propane trimethacrylate, tripropylene glycol diacrylate, diallyl ether, diallylamine, diallyl carbonate, N,Nxe2x80x2-diallylurea, triallylamine, tris(2-methylallyl)amine, 2,4,6-triallyloxy-1,3,5-triazine, triallyl-s-triazine-2,4,6(1H,3H,5H)trione, diallylmalonic esters, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate and poly(propylene glycol) methacrylate. This list is illustrative, and not limiting.
However, the silicone materials according to the invention preferably contain, as constituent (A), an aliphatically unsaturated organosilicon compound, it being possible to use all aliphatically unsaturated organosilicon compounds used to date in addition-crosslinking materials including, for example, silicone block copolymers having urea segments, silicone block copolymers having amide segments and/or imide segments and/or ester-amide segments and/or polystyrene segments and/or silarylene segments and/or carborane segments and silicone graft copolymers having ether groups.
Linear or branched organopolysiloxanes comprising units of the formula
RaR1bSiO(4xe2x88x92axe2x88x92b)/2xe2x80x83xe2x80x83(I)
in which
R may be identical or different and denotes an organic radical free of aliphatic carbon-carbon multiple bonds,
R1 may be identical or different and denotes a monovalent, optionally substituted, SiC-bonded hydrocarbon radical having an aliphatic carbon-carbon multiple bond,
a is 0, 1, 2 or 3 and
b is 0, 1 or 2,
with the proviso that the sum a+b is less than or equal to 3 and on average at least 2 radicals R1, are present per molecule, are preferably used as organosilicon compounds (A) which have SiC-bonded radicals having aliphatic carbon-carbon multiple bonds.
Radicals R may be monovalent or polyvalent radicals, the polyvalent radicals, such as bivalent, trivalent and tetravalent radicals, thus linking together a plurality of silyloxy units of the formula (I), such as, two, three or four of said silyloxy units. R also may be a monovalent radical such as xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94OR6, xe2x80x94CN, xe2x80x94SCN, xe2x80x94NCO and SiC-bonded optionally substituted hydrocarbon radicals optionally interrupted by oxygen atoms or the group xe2x80x94C(O)xe2x80x94, and divalent radicals Si-bonded on both sides according to formula (I).
If radical R denotes SiC-bonded, substituted hydrocarbon radicals, preferred substituents are halogen atoms, phosphorus-containing radicals, cyano radicals, xe2x80x94OR6, xe2x80x94NR6xe2x80x94, NR62, xe2x80x94NR6xe2x80x94C(O)xe2x80x94NR62, xe2x80x94C(O)xe2x80x94NR62, xe2x80x94C(O)xe2x80x94R6, xe2x80x94C(O)OR6, xe2x80x94SO2xe2x80x94Ph and xe2x80x94C6F5, in which R6 has the abovementioned meaning and Ph is a phenyl radical.
Examples of radicals R are alkyl radicals such as the methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl and tert-pentyl radicals; hexyl radicals such as the n-hexyl radical; heptyl radicals such as the n-heptyl radical; octyl radicals such as the n-octyl radical and isooctyl radicals, for example the 2,2,4-trimethylpentyl radical; nonyl radicals such as the n-nonyl radical; decyl radicals such as the n-decyl radical; dodecyl radicals such as the n-dodecyl radical; and octadecyl radicals such as the n-octadecyl radical; cycloalkyl radicals such as cyclopentyl, cyclohexyl, cycloheptyl and methylcyclohexyl radicals; aryl radicals such as the phenyl, naphthyl, anthryl and phenanthryl radicals; alkaryl radicals such o-, m-, and p-tolyl radicals, xylyl radicals and ethylphenyl radicals; and aralkyl radicals such as the benzyl radical and the xcex1- and xcex2-phenylethyl radicals.
Examples of substituted radicals R are haloalkyl radicals, such as the 3,3,3-trifluoro-n-propyl radical, the 2,2,2,2xe2x80x2,2xe2x80x2,2xe2x80x2-hexafluoroisopropyl radical, the heptafluoroisopropyl radical, haloaryl radicals, such as the o-, and p-chlorophenyl. radical, xe2x80x94(CH2)nxe2x80x94N(R6)C(O)NR62, xe2x80x94(CH2)nxe2x80x94C(O)NR62, xe2x80x94(CH2)nxe2x80x94C(O)R6, xe2x80x94(CH2)nxe2x80x94C(O)OR6, xe2x80x94(CH2)nxe2x80x94C(O)NR62, xe2x80x94(CH2)nxe2x80x94C(O)xe2x80x94(CH2)mxe2x80x94C(O)CH3, xe2x80x94(CH2)nxe2x80x94NR6xe2x80x94(CH2)mxe2x80x94NR62, xe2x80x94(CH2)nxe2x80x94Oxe2x80x94COxe2x80x94R6, xe2x80x94(CH2)nxe2x80x94Oxe2x80x94(CH2)mxe2x80x94CH(OH)xe2x80x94CH2OH, xe2x80x94(CH2)nxe2x80x94(OCH2CH2)mxe2x80x94OR6, xe2x80x94(CH2)nxe2x80x94SO2xe2x80x94Ph and xe2x80x94(CH2)nxe2x80x94Oxe2x80x94C6F5, in which R6 has the meanings stated therefor above, n and m are identical or different integers between 0 and 10 and Ph designates the phenyl radical.
Examples of divalent radicals R Si-bonded on both sides according to Formula (I) are those which are derived from the monovalent examples stated above for radical R by providing an additional bond by substitution of a hydrogen atom. Examples of such radicals are xe2x80x94(CH2)nxe2x80x94, xe2x80x94CH(CH3)xe2x80x94, xe2x80x94C(CH3)2xe2x80x94, xe2x80x94CH(CH3)xe2x80x94CH2xe2x80x94, xe2x80x94C6H4xe2x80x94, xe2x80x94CH(Ph)xe2x80x94CH2xe2x80x94, xe2x80x94C(CF3)2xe2x80x94, xe2x80x94(CH2)nxe2x80x94C6H4xe2x80x94(CH2)nxe2x80x94, xe2x80x94(CH2)nxe2x80x94C6H4xe2x80x94C6H4xe2x80x94(CH2)nxe2x80x94xe2x80x94(CH2O)mxe2x80x94, xe2x80x94(CH2CH2O)mxe2x80x94, xe2x80x94(CH2)nxe2x80x94Oxxe2x80x94C6H4xe2x80x94SO2xe2x80x94C6H4xe2x80x94Oxxe2x80x94(CH2)nxe2x80x94, in which x is 0 or 1, m and n have the abovementioned meaning and Ph is a phenyl radical.
Radical R is preferably a monovalent, SiC-bonded, optionally substituted hydrocarbon radical free of aliphatic carbon-carbon multiple bonds and having 1 to 18 carbon atoms, particularly preferably a monovalent, SiC-bonded hydrocarbon radical free of aliphatic carbon-carbon multiple bonds and having 1 to 6 carbon atoms, in particular the methyl or phenyl radical.
Radical R1 may be one of any desired groups susceptible to addition reaction (hydrosilylation) with a compound having SiH functional groups. If R1 is an SiC-bonded, substituted hydrocarbon radical, the preferred substituents are halogen atoms, cyano radicals and xe2x80x94OR6, in which R6 has the abovementioned meaning. Radical R1 is preferably an alkenyl or alkynyl group having 2 to 16 carbon atoms, such as a vinyl, allyl, methallyl, 1-propenyl, 5-hexenyl, ethynyl, butadienyl, hexadienyl, cyclopentenyl, cyclopentadienyl, cyclohexenyl, vinylcyclohexylethyl, divinylcyclohexylethyl, norbornenyl, vinylphenyl, or styryl radical, the vinyl, allyl and hexenyl radicals being particularly preferred.
The molecular weight of constituent (A) may vary within wide limits, for example between 102 and 106 g/mol. The constituent (A) may be, for example, a relatively low molecular weight oligosiloxane having alkenyl functional groups, such as 1,2-divinyltetramethyldisiloxane, but may also be a highly polymeric polydimethylsiloxane having Si-bonded vinyl groups in the chain or as terminal groups and, for example, having a molecular weight of 105 g/mol (number average determined by means of NMR). The structure of the molecules forming the constituent (A) has also not been established; in particular, the structure of a relatively high molecular weight, i.e. oligomeric or polymeric, siloxane may be linear, cyclic, branched, resin-like, or network-like. Linear and cyclic polysiloxanes are preferably composed of units of the formula R3SiO1/2, R1R2SiO2/2, R1RSiO2/2 and R2SiO2/2, in which R and R1 have the abovementioned meaning. Branched and network-like polysiloxanes additionally contain trifunctional and/or tetrafunctional units, those of the formulae RSiO3/2, R1SiO3/2 and SiO4/2 being preferred. Of course, mixtures of different siloxanes fulfilling the criteria of the constituent (A) may also be used.
Essentially linear polydiorganosiloxanes having vinyl functional groups and a viscosity of from 0.01 to 500,000 Paxc2x7s, more preferably from 0.1 to 100,000 Paxc2x7s, in each case at 25xc2x0 C., are preferred as component (A).
All organosilicon compounds which have silicon bonded hydrogen functional (Si-H) groups can be used as organosilicon compound (B).
Linear, cyclic or branched organopolysiloxanes comprising units of the formula
RcHdSiO(4xe2x88x92cxe2x88x92d)/2xe2x80x83xe2x80x83(II)
in which
R may be identical or different and has the abovementioned meaning,
c is 0, 1, 2 or 3 and
d is 0, 1 or 2,
with the proviso that the sum of c+d is less than or equal to 3 and on average at least two Si-bonded hydrogen atoms are present per molecule, are preferably used as organopolysiloxanes (B) which have Si-bonded hydrogen atoms. Preferably, the organopolysiloxane (B) used according to the invention contains Si-bonded hydrogen in the range from 0.04 to 1.7% by weight, based on the total weight of the organopolysiloxane (B).
The molecular weight of constituent (B) can likewise vary within wide limits, for example between 102 and 106 g/mol. Thus, constituent (B) may be, for example, a relatively low molecular weight oligosiloxane having SiH functional groups, such as tetramethyldisiloxane, but may also be a highly polymeric polydimethylsiloxane having SiH groups in the chain, or having terminal SiH groups, or may be a silicone resin having SiH groups. The structure of the molecules forming the constituent (B) is also not fixed; in particular, the structure of a relatively high molecular weight, i.e. oligomeric or polymeric SiH-containing siloxane may be linear, cyclic, branched, resin-like, or network-like. Linear and cyclic polysiloxanes are preferably composed of units of the formula R3SiO1/2, HR2SiO1/2, HRSiO2/2 and R2SiO2/2, in which R has the abovementioned meaning. Branched and network-like polysiloxanes additionally contain trifunctional and/or tetrafunctional units, those of the formulae RSiO3/2, HSiO3/2 and SiO4/2 being preferred. Of course, mixtures of different siloxanes fulfilling the criteria of constituent (B) may also be used. In particular, the molecules forming the constituent (B) may optionally simultaneously also contain aliphatically unsaturated groups in addition to the obligatory SiH groups. The use of low molecular weight compounds having SiH functional groups, such as tetrakis(dimethylsiloxy)silane and tetramethylcyclotetrasiloxane, and relatively high molecular weight SiH-containing siloxanes, such as poly(hydrogenmethyl)siloxane and poly(dimethylhydrogenmethyl)siloxane, having a viscosity at 25xc2x0 C. of 10 to 10,000 mPaxc2x7s, or analogous SiH-containing compounds in which some of the methyl groups have been replaced by 3,3,3-trifluoropropyl or phenyl groups are particularly preferred.
Constituent (B) is preferably contained in the total crosslinkable silicone materials according to the invention in an amount such that the molar ratio of SiH groups to aliphatically unsaturated groups is from 0.1 to 20, particularly preferably between 1.0 and 5.0.
The components (A) and (B) used according to the invention are commercial products or can be prepared by processes customary in chemistry.
Instead of or in addition to components (A) and (B), the materials according to the invention may contain organopolysiloxanes (C) which have aliphatic carbon-carbon multiple bonds and Si-bonded hydrogen atoms. The use of such multi-functional compounds, however, is not preferred. If siloxanes (C) are used, they are preferably those comprising units of the formulae
RgSiO4xe2x88x92g/2, RhR1SiO3xe2x88x92h/2 and RiHSiO3xe2x88x92i/2,
in which R and R1 have the meanings stated above therefor, and
g is 0, 1, 2 or 3,
h is 0, 1 or 2 and
i is 0, 1 or 2,
with the proviso that at least 2 radicals R1 and at least two Si-bonded hydrogen atoms are present per molecule.
Examples of organopolysiloxanes (C) are those comprising SiO4/2, R3SiO1/2, R2R1SiO1/2 and R2HSiO1/2 units, so-called MQ resins, it being possible for these resins additionally to contain RSiO3/2 and R2SiO units, and linear organopolysiloxanes essentially consisting of R2R1SiO1/2, R2SiO and RHSiO units, in which R and R1 have the abovementioned meaning. The organopolysiloxanes (C) preferably have an average viscosity of from 0.01 to 500,000 Paxc2x7s, particularly preferably 0.1 to 100,000 Paxc2x7s, in each case at 25xc2x0 C. Organopolysiloxanes (C) can be prepared by methods customary in chemistry.
Examples of R2 are dienes, such as 1,3-butadiene, 1,4-diphenyl-1,3-butadiene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, 2,4-hexadiene, 1,4-hexadiene, 1,5-hexadiene, 2,5-dimethyl-2,4-hexadiene, xcex1- and xcex3-terpinene, (R)-(+)-4-isopropenyl-1-methyl-1-cyclohexene, (S)-(xe2x88x92)-4-isopropenyl-1-methyl-1-cyclohexene, 4-vinyl-1-cyclohexene, 2,5-heptadiene, 1,5-cyclooctadiene, 1-chloro-1,5-cyclooctadiene, 1,5-dimethyl-1,5-cyclooctadiene, 1,6-dimethyl-1,5-cyclooctadiene, 1,5-dichloro-1,5-cyclooctadiene, 5,8-dihydro-1,4-dioxocine, xcex74-1,3,5,7-cyclooctatetraene, xcex74-1,3,5-cycloheptatriene, xcex74-1-fluoro-1,3,5,7-cyclooctatetraene, xcex74-1,2,4,7-tetramethyl-1,3,5,7-cyclooctatetraene, 1,8-cyclotetradecadiene, 1,9-cyclohexadecadiene, 1,13-cyclotetracosadiene, xcex74-1,5,9-cyclododecatriene, xcex74-1,5,10-trimethyl-1,5,9-cyclododecatriene, xcex74-1,5,9,13-cyclohexadecatetraene, bicyclo[2.2. 1]hepta-2,5-diene, 1,3-dodecadiene, methylcyclopentadiene dimer, 4,7-methylene-4,7,8,9-tetrahydroindene, bicyclo[4.2.2]deca-3,9-diene-7,8-dicarboxylic anhydride, alkyl bicyclo[4.2.2]deca-3,9-diene-7,8-dicarboxylate and alkyl bicyclo[4.2.2]deca-3,7,9-triene-7,8-dicarboxylate.
Diene R2 is preferably 1,5-cyclooctadiene, 1,5-dimethyl-1,5-cyclooctadiene, 1,6-dimethyl-1,5-cyclooctadiene, 1-chloro-1,5-cyclooctadiene, 1,5-dichloro-1,5-cyclooctadiene, 1,8-cyclotetradecadiene, 1,9-cyclohexadecadiene, 1,13-cyclotetracosadiene, bicyclo[2.2.1]hepta-2,5-diene, 4-vinyl-1-cyclohexene and xcex74-1,3,5,7-cyclooctatetraene, 1,5-cyclooctadiene, bicyclo[2.2.1]hepta-2,5-diene, with 1,5-dimethyl-1,5-cyclooctadiene and 1,6-dimethyl-1,5-cyclooctadiene being particularly preferred.
Examples of R3 are alkyl radicals such as the methyl, ethyl, n-propyl, isopropyl, 1-n-butyl, 2-n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl and tert-pentyl radicals; hexyl radicals such as the n-hexyl radical; heptyl radicals such as the n-heptyl radical; octyl radicals such as the n-octyl radical and the isooctyl radicals, for example the 2,2,4-trimethylpentyl radical; nonyl radicals such as the n-nonyl radical; decyl radicals such as the n-decyl radical; cycloalkyl radicals such as the cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and methylcyclohexyl radicals; unsaturated radicals such as the allyl, 5-hexenyl, 7-octenyl, cyclohexenyl and styryl radicals; aryl radicals such as phenyl radicals, o-, m- and p-tolyl radicals, xylyl radicals and ethylphenyl radicals; aralkyl radicals such as the benzyl radical and the xcex1- and xcex2-phenylethyl radicals; and radicals of the formula xe2x80x94C(R1)xe2x95x90CR12. Further examples of R3 are xe2x80x94OR6 radicals such as hydroxy, methoxy, ethoxy, isopropoxy, butoxy and phenoxy radicals. Examples of halogenated radicals R3 are haloalkyl radicals such as the 3,3,3-trifluoro-n-propyl radical, the 2,2,2,2xe2x80x2,2xe2x80x2,2xe2x80x2-hexafluoroisopropyl radical, and the heptafluoroisopropyl radical; and haloaryl radicals such as the o-, m- and p-chlorophenyl radicals. Examples of silyl radicals R3 are trirnethylsilyl, ethyldimethylsilyl, methoxydimethylsilyl, n-propyldimethylsilyl, isopropyldimethylsilyl, n-butyldimethylsilyl, tert-butyldimethylsilyl, octyldimethylsilyl, vinyldimethylsilyl, phenyldimethylsilyl, diphenylmethylsilyl, hydroxypropyldimethylsilyl, methylvinylphenylsilyl and methoxypropylsilyl radicals.
Radical R3 is preferably a hydrogen atom, a hydroxyl radical, a methoxy radical, a hydrocarbon radical having 1 to 8 carbon atoms, a trimethylsilyl, ethyldimethylsilyl, butyldimethylsilyl, or octyldimethylsilyl radical, with a hydrogen atom, the methyl radical and the trimethylsilyl radical being particularly preferred.
R4 is preferably a monovalent hydrocarbon radical having 1 to 24 carbon atoms, such as the examples stated in connection with radical R3, substituted hydrocarbon radicals such as the hydroxypropyl and chloropropyl radical and xe2x80x94OR6 radicals such as hydroxyl, methoxy and ethoxy radicals, with the methyl, ethyl, butyl, octyl, methoxy, ethoxy and hydroxypropyl radicals being particularly preferred.
Examples of R6 are the radicals stated for R3. R6 is preferably hydrogen, an alkyl radical, or an aryl radical, with a hydrogen atom, the methyl radical and the ethyl radical being particularly preferred.
Examples of radical R7 are the radicals stated for radical R3, and the 1-trimethylsilyloxypropyl-3-dimethylsilyl, 1-ethyldimethylsilyloxypropyl-3-dimethylsilyl, 1-methoxydimethylsilyloxypropyl-3-dimethylsilyl and pentamethyldisiloxanyl radicals. R7 are preferably monovalent radicals, for example, a hydrogen atom, or the methyl, methoxy, trimethylsilyl, octyldimethylsilyl, dimethyhnethoxysilyl, 1-trimethylsilyloxypropyl-3-dimethylsilyl or hydroxypropyldimethylsilyl radicals, or a polyvalent radicals such as xe2x80x94C2H4xe2x80x94, xe2x80x94Si(Me)2xe2x80x94Oxe2x80x94Si(Me)2O1/2, xe2x80x94Si(Me)2xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94Oxe2x80x94Si(Me)2O1/2, xe2x80x94Si(Me)2xe2x80x94Oxe2x80x94Si(Me)O2/2, xe2x80x94Si(Me)2xe2x80x94Oxe2x80x94SiO3/2, xe2x80x94Si(Me)2xe2x80x94CH2xe2x80x94CH2xe2x80x94Si(Me)2O1/2 and xe2x80x94Si(Me)2xe2x80x94CH2xe2x80x94CH2xe2x80x94Si(Me)O2/2, in which Me denotes a methyl radical.
Examples of radicals R8 are an oxygen atom and xe2x80x94CH2xe2x80x94, xe2x80x94C2H4xe2x80x94, xe2x80x94C3H6xe2x80x94, xe2x80x94C4H8xe2x80x94, xe2x80x94C6H12xe2x80x94, xe2x80x94C6H4xe2x80x94, xe2x80x94CH2CH(CH3)xe2x80x94C6H4xe2x80x94CH(CH3)CH2xe2x80x94 and xe2x80x94(CH2)3Oxe2x80x94, with the oxygen atom, and the xe2x80x94C2H4xe2x80x94, xe2x80x94C3H6xe2x80x94 and xe2x80x94(CH2)3)xe2x80x94 diradicals being particularly preferred.
Examples of radicals R9 are a hydrogen atom and the examples stated for radical R and radical R1. R9 are preferably monovalent hydrocarbon radicals with 1 to 12 carbon atoms, the methyl, ethyl, phenyl and vinyl radicals being particularly preferred. In all these descriptions of various replacement groups for R1 through R9, the exemplified radicals are illustrative, and not limiting.
Examples of the units of the formula (VI) are SiO4/2, (Me)3SiO1/2, Vi(Me)2SiO1/2, Ph(Me)2SiO1/2, (Me)2SiO2/2, Ph(Me)SiO2/2, Vi(Me)SiO2/2, H(Me)SiO2/2, MeSiO3/2, PhSiO3/2, ViSiO3/2, (Me)2(MeO)SiO1/2 and OH(Me)2SiO1/2, with (Me)3SiO1/2, Vi(Me)2SiO1/2, (Me)2SiO2/2, Ph(Me)SiO2/2, Vi(Me)SiO2/2 and Me2(MeO)SiO1/2xe2x80x94MeSiO3/2 being preferred, and with (Me)3SiO1/2, Vi(Me)2SiO1/2, (Me)2SiO2/2 and Vi(Me)SiO2/2 being particularly preferred. In these formulae, Me is a methyl radical, Vi is a vinyl radical and Ph is a phenyl radical.
A limited number of bis(alkynyl)(xcex7-olefm)platinum compounds and processes for their preparation are known from J. Chem. Soc., Dalton Trans. (1986) 1987-92 and Organometallics (1992) 11 2873-2883. The platinum catalysts (D) according to the invention can be prepared by analogous syntheses and purification steps.
The platinum catalyst (D) used according to the invention is preferably a bis(alkynyl))(1,5-cyclooctadienyl)platinum, bis(alkynyl)(bicyclo[2.2. 1]hepta-2,5-dienyl)platinum, bis(alkynyl) (1,5-dimethyl-1,5-cyclooctadienyl)platinum or bis(alkynyl)(1,6-dimethyl-1,5-cyclooctadienyl)platinum complex.
The present invention furthermore relates to platinum complexes of the formula (III) and platinum complexes comprising structural units of the formulae (V) and optionally (VI), those in which R2 are cyclic dienes having 6 to 28 carbon atoms being preferred.
The amount of the platinum catalyst (D) used according to the invention depends on the desired crosslinking rate and on the respective use and economics with respect thereto. The materials according to the invention contain platinum catalysts (D) in amounts of preferably, from 0.05 to 500 ppm by weight (=parts by weight per million parts by weight), more preferably from 0.5 to 100 ppm by weight, and in particular from 1 to 50 ppm by weight, based in each case on the total weight of the material.
In addition to the components (A) to (D), the curable compositions according to the invention may also contain all further substances which have also been used to date for the preparation of addition-crosslinkable materials.
Examples of reinforcing fillers which may be used as component (E) in the materials according to the invention are pyrogenic or precipitated silicic acids having BET surface areas of at least 50 m2/g and carbon blacks and active carbons, such as furnace black and acetylene black, pyrogenic and precipitated silicic acids having BET surface areas of at least 50 m2/g being preferred. These silicic acid fillers may have a hydrophilic character or may be rendered hydrophobic by known methods. When hydrophilic fillers are used, the addition of a water repellant agent is required. The content of actively reinforcing filler (E) in the crosslinkable material according to the invention is in the range from 0 to 70% by weight, preferably 0 to 50% by weight.
The silicone rubber material according to the invention can alternatively contain, as constituent (F), further additives in an amount of up to 70% by weight, preferably from 0.0001 to 40% by weight. These additives may be, for example, inactive fillers, resin-like polyorganosiloxanes which differ from the siloxanes (A), (B) and (C), dispersants, solvents, adhesion promoters, pigments, dyes, plasticizers, organic polymers, heat stabilizers, etc. These include additives such as quartz powder, diatomaceous earth, clays, chalk, lithopone, carbon blacks, graphite, metal oxides, metal carbonates, metal sulfates, metal salts of carboxylic acids, metal dusts, fibers, such as glass fibers, plastics fibers, plastics powder, dyes, pigments, etc.
Furthermore, additives (G) which serve for specifically controlling the processing time, initiation temperature and crosslinking rate of the materials according to the invention may also be present. These inhibitors and stabilizers are very well known in the area of addition-crosslinking materials. Examples of customary inhibitors are acetylenic alcohols, such as 1-ethynyl-2-cyclohexanol, 2-methyl-3-butyn-2-ol, 3,5-dimethyl-1-hexyn-3-ol, and 3-methyl-1-dodecyn-3-ol; polymethylvinylcyclosiloxanes; such as 1,3,5,7-tetravinyltetramethyltetrayclosiloxane; low molecular weight silicone oils having methylvinyl-SiO2/2 groups and/or R2-vinyl-SiO1/2 terminal groups such as divinyltetramethyldisiloxane and tetravinyldimethyldisiloxane; trialkyl cyanurates; alkyl maleates; such as diallyl maleate, dimethyl maleate and diethyl maleate; alkyl fumarates such as diallyl fumarate and diethyl fumarate; organic hydroperoxides such as cumyl hydroperoxide, tert-butyl hydroperoxide and pinane hydroperoxides; organic peroxides; organic sulfoxides; organic amines, diamines and amides; phosphines and phosphites; nitriles, triazoles, diaziridines and oximes. The effect of these inhibitor additives (G) depends on their chemical structure, so that their concentrations in the compositions must be determined individually.
The inhibitor content of the materials according to the invention is preferably from 0 to 50,000 ppm, particularly preferably from 20 to 2000 ppm, in particular from 100 to 1000 ppm.
The organopolysiloxane materials according to the invention can, if required, be dissolved, dispersed, suspended or emulsified in liquids. The materials according to the invention may in particular depending on the viscosity of the constituents and filler content, have a low viscosity and be pourable, may have a pasty consistency, may be pulverulent or may be pliable, highly viscous materials, such physical embodiments being ordinarily the case with the materials denoted by those skilled in the art as RTV-1, RTV-2, LSR and HTV. If the compositions are highly viscous, the materials according to the invention can be prepared in the form of granules. Here, the individual granular particle may contain all components, or the components D and B may be incorporated separately into different granular particles. Regarding the elastomeric properties of the crosslinked silicone materials according to the invention, the entire spectrum is likewise included, beginning with extremely soft silicone gels, through rubber-like materials, to highly crosslinked silicones exhibiting glassy behavior.
The preparation of the organopolysiloxane materials according to the invention can be carried out by known processes, such as, for example, by uniform mixing of the individual components. Any desired sequence may be employed, but the uniform mixing of the platinum catalyst (D) with a mixture of (A), (B), optionally (E), (F) and (G) is preferable. The platinum catalyst (D) used according to the invention can be incorporated as a solid substance or as a solution, dissolved in a suitable solvent, or as a so-called master-batch, in which the catalyst (D) is uniformly mixed with a small amount of (A) or (A) with (E). The mixing is effected as a function of the viscosity of (A), for example by means of a stirrer, in a dissolver, on a roll or in a kneader. The catalyst (D) can also be encapsulated in an organic thermoplastic or thermoplastic silicone resin.
The components (A) to (G) used according to the invention may each be an individual component, or a mixture of at least two different types of such component.
The materials according to the invention which can be crosslinked by addition of an Si-bonded hydrogen at an aliphatic multiple bond can be allowed to crosslink under conventional conditions. Temperatures of from 100xc2x0 C. to 220xc2x0 C., more preferably from 130xc2x0 C. to 190xc2x0 C., and a pressure of from 900 hPa to 1100 hPa are preferably used here. However, higher or lower temperatures and pressures may also be used. The crosslinking can also be carried out photochemically by means of high-energy radiation, such as, for example, visible light having short wavelengths and UV light, or by a combination of thermal and photochemical excitation.
The present invention furthermore relates to moldings prepared by crosslinking the materials according to the invention.
The materials according to the invention and the crosslinked products produced therefrom according to the invention can be used for all purposes for which organopolysiloxane materials crosslinkable to elastomers or elastomers have previously been used. This includes, for example, silicone coating or impregnation of any desired substrates, the production of shaped articles, for example by the injection molding method, vacuum extrusion method, extrusion method, molding and compression molding, casting, and use as sealing, embedding and casting materials, etc.
The crosslinkable materials according to the invention have the advantage that they can be prepared in a simple process using readily obtainable starting materials and hence may be economically prepared. The crosslinkable materials according to the invention have the further advantage that, as a one-component formulation, they have a good shelf life at 25xc2x0 C. and ambient pressure, and crosslink rapidly only at elevated temperature. The silicone materials according to the invention have the still further advantage that, in the case of two-component formulation, after mixing of the two components, they give a crosslinkable silicone material whose processibility is retained over a long period at 25xc2x0 C. and ambient pressure (extremely long pot life) and which crosslinks rapidly only at elevated temperature.
In the preparation of the crosslinkable materials according to the invention, it is a major advantage that the platinum catalyst (D) can be readily incorporated and no solvent is required for this purpose. The materials according to the invention furthermore have the advantage that the crosslinked silicone rubbers have excellent transparency. The materials according to the invention also have the advantage that the hydrosilylation reaction does not slow down with the duration of the reaction, nor even after long storage at room temperature.
The platinum complexes according to the invention are useful as catalysts for the well-known hydrosilylation reaction in organosilicon chemistry, as a catalyst for the hydrogenation of unsaturated organic compounds or polymers, and for the oligomerization of acetylene and other alkynes. The platinum catalysts according to the invention furthermore have the advantage that terminal double bonds do not undergo rearrangement to become internal double bonds in the hydrosilylation reaction, with the result that weakly reactive isomerized starting material would remain. The platinum catalysts according to the invention have the further advantage that no platinum colloids are formed and no discolorations result through their use.
In the examples described below, all data on parts and percentages are based on weight, unless stated otherwise. Unless stated otherwise, the following examples are carried out at a pressure of the ambient atmosphere, i.e. at about 1000 hPa, and at room temperature, i.e. at about 20xc2x0 C., or at a temperature which is established on combining the reactants at room temperature without additional heating or cooling.
Below, all viscosity data are based on a temperature of 25xc2x0 C.
COD denotes cycloocta-1,5-diene, ME2COD denotes a mixture of 1,5-dimethylcycloocta-1,5-diene and 1,6-dimethylcycloocta-1,5-diene,
p- denotes para substitution on an aromatic ring,
m- denotes meta substitution on an aromatic ring,
Vi denotes a vinyl radical,
Me denotes a methyl radical and
Ph denotes a phenyl radical.
A suspension of 0.50 g of [PtCl2(COD)] in 20 ml of methanol was cooled to xe2x88x9220xc2x0 C. under nitrogen. A freshly prepared solution of 0.77 g of (4-trimethylsilylphenylethynyl)trimethylsilane (prepared according to J. Chem. Soc. (C) 1967, 1364-1366) and sodium methanolate (prepared from 61.5 mg of sodium and 15 ml of methanol) was then slowly added dropwise. After about 20 minutes, the mixture was heated to room temperature, and the precipitate was filtered off and was washed five times with acetone. 0.78 g of a platinum complex of the following formula was obtained:
[(COD)Pt(p-Cxe2x89xa1Cxe2x80x94C6H4xe2x80x94SiMe3)2]
Under analogous conditions, catalyst 1 can also be prepared using 4-trimethylsilylphenylacetylene instead of (4-trimethylsilylphenylethynyl)trimethylsilane.
A suspension of 0.50 g of [PtCl2(COD)] in 20 ml of methanol was cooled to xe2x88x9220xc2x0 C. under nitrogen. A freshly prepared solution of 0.77 g of (3-trimethylsilylphenylethynyl)trimethylsilane (prepared according to J. Chem. Soc. (C) 1967, 1364-1366) and sodium methanolate (prepared from 61.5 mg of sodium and 15 ml of methanol) was then slowly added dropwise. After about 20 minutes, the mixture was heated to room temperature, and the precipitate was filtered off and was washed five times with acetone. 0.81 g of a platinum complex of the following formula was obtained:
[(COD)Pt(m-Cxe2x89xa1Cxe2x80x94C6H4xe2x80x94SiMe3)2]
A suspension of 0.50 g of [PtCl2(COD)] in 15 ml of methanol was cooled to xe2x88x9220xc2x0 C. under nitrogen. A freshly prepared solution of 0.84 g of (4-dimethyloctylsilylphenylacetylene (preparation analogous to J. Chem. Soc. (C) 1967, 1364-1366, n-octyldimethylchlorosilane being used instead of trimethylchlorosilane) and sodium methanolate (prepared from 61.5 mg of sodium and 15 ml of methanol) was then slowly added dropwise. After about 60 minutes, the mixture was heated to room temperature, and the precipitate was filtered off and was washed five times with acetone. 0.84 g of a platinum complex of the following formula was obtained:
{(COD)Pt[p-Cxe2x89xa1Cxe2x80x94C6H4xe2x80x94SiMe2xe2x80x94(CH2)7xe2x80x94CH3]2}
The procedure described above for the preparation of catalyst 1 is repeated with the modification that 0.54 g of [PtCl2(Me2COD)] was used instead of 0.50 g of [PtCl2(COD)]. 0.73 g of the platinum complex of the following formula was obtained:
[(Me2COD)Pt(p-Cxe2x89xa1Cxe2x80x94C6H4xe2x80x94SiMe3)2]
A suspension of 0.50 g of [PtCl2(COD)] in 20 ml of methanol was cooled to xe2x88x9220xc2x0 C. under nitrogen. A freshly prepared solution of 0.72 g of (4-dimethylsilylphenylethynyl)trimethylsilane (prepared analogously to J. Chem. Soc. (C) 1967, 1364-1366, dimethylchlorosilane (commercially available from ABCR GmbH and Co. KG used in lieu of chlorotrimethylsilane) and sodium methanolate (prepared from 61.5 mg of sodium and 15 ml of methanol) was then slowly added dropwise. After about 60 minutes, the mixture was heated to room temperature, and the precipitate was filtered off, stirred in acetone, again filtered and dried in vacuo. 0.83 g of a platinum complex of the following formula was obtained:
[(COD)Pt(p-Cxe2x89xa1Cxe2x80x94C6H4xe2x80x94SiMe2OMe)2]
A suspension of 0.50 g of [PtCl2(COD)] in 20 ml of methanol was cooled to xe2x88x9220xc2x0 C. under nitrogen. A freshly prepared solution of 1.2 g of (4-trimethylsilyloxypropylphenylethynyl)trimethylsilane (prepared analogously to J. Chem. Soc. (C) 1967, 1364-1366, 3-(trimethylsilyloxypropyl)dimethylchlorosilane (commercially available from ABCR GmbH and Co. KG) being used instead of chlorotrimethylsilane) and sodium methanolate (prepared from 61.5 mg of sodium and 15 ml of methanol) was then slowly added dropwise. After about 20 minutes, the mixture was heated to room temperature, and the precipitate was filtered off, stirred in acetone, filtered off and dried in vacuo. 0.99 g of a platinum complex of the following formula was obtained:
[(COD)Pt(p-Cxe2x89xa1Cxe2x80x94C6H4xe2x80x94SiMe2CH2CH2CH2OH)2]
0.5 g of catalyst 6 was suspended in diethyl ether, and 1.13 ml of butyllithium (1.6 M in hexane fraction, obtainable from Sigma-Aldrich Chemie GmbH) was added at 79xc2x0 C. After thawing at 0xc2x0 C., 0.15 g of vinyldimethylchlorosilane (obtainable from ABCR GmbH and Co. KG) was added dropwise and stirring was carried out for 1 hour. Thereafter, the mixture was evaporated to dryness, taken up in toluene, filtered off from the LiCl and once again evaporated to dryness. 0.47 g of a platinum complex with the following formula was obtained:
[(COD)Pt(p-Cxe2x89xa1Cxe2x80x94C6H4xe2x80x94SiMe2CH2CH2CH2OSiMe2Vi)2]
2.08 g of silanol-terminated polydimethylsiloxane having on average 0.8% by weight of SiOH groups (obtainable from ABCR GmbH and Co. KG), 1.0 g of catalyst 5 and 0.02 g of dibutyl phosphate (obtainable from Sigma-Aldrich Chemie GmbH) were stirred for 2 hours, 0.013 g of titanium(IV) butylate (obtainable from Sigma-Aldrich Chemie GmbH) was then stirred in, and the mixture was filtered. 2.3 g of a platinum complex were obtained, which, according to 1H- and 29Si-NMR, had on average the following formula (any residues of a titanium phosphate compound still present do not present any problems):
{[(COD)Pt(p-Cxe2x89xa1Cxe2x80x94C6H4xe2x80x94SiMe2OMe) [p-Cxe2x89xa1Cxe2x80x94C6H4(xe2x80x94SiMe2O)59xe2x80x94SiMe2xe2x80x94C6H4xe2x80x94Cxe2x89xa1Cxe2x80x94p]Pt(COD)[p-Cxe2x89xa1Cxe2x80x94C6H4(xe2x80x94SiMe2O)59xe2x80x94SiMe2xe2x80x94C6H4xe2x80x94Cxe2x89xa1Cxe2x80x94p)Pt(COD)(p-Cxe2x89xa1Cxe2x80x94C6H4xe2x80x94SiMe2OMe)}